Antenna Hidden

[rbh]

Re: Antenna Hidden

50 watts naa,
50 thousand watts yaa, pumpin the wattage it your cottage.
any one played around with the old an-grc 106 sets?
rob

 

[Lyle29464]

Re: Antenna Hidden

50 watts naa,
50 thousand watts yaa, pumpin the wattage it your cottage.
any one played around with the old an-grc 106 sets?
rob

a little bit. went to armchair school in fort sill. worked on most of the army/navy stuff.

 

[Pez Vela]

Re: Antenna Hidden

How about a 4' black one?

 

[Boatist]

Re: Antenna Hidden

Two things to note. First a 8 foot antenna under the gunnels will be transmiting straight up into the sky and into the water and a narrow band to each side of the boat only. nothing toward the Bow or Stern.

Also with the antenna in there other metal or wireing will pick up the signal and reflect back to the antenna causeing a high SWR and that can shut down the transmiter or damage the radio. Most radio today will have circuits to protect the transmitter bye shuting it down.

Also some of the wireing could cause other thing to malfunction. Things like depth finders or rpm guages.

Even with the antenna mounted properly the range of a 8 foot 6 db gain antenna will be less than 5 miles plus the the range of the other station. So boat to boat about 10 miles on average.

One last point, in an emergency where you need to put out a "MayDay Call' the last thing you are going to want to do is get the antenna out to make the call. You would much rather be stopping the water from coming in and bailing out the boat with a big bucket or putting out the fire. Of course you would also want to give the Coast Guard and other boats near you your position.

Mount it properly it could save the life of you and your crew.

You can dress it up with a small flag or a Bikini Top.

 

[amanphoto]

Re: Antenna Hidden

Can I hide it in my Bimini top? If I put it inside one of the vertical metal tubes that make up the Bimini will it increase my range or decrease it?

 

[Knightgang]

Re: Antenna Hidden

Even with the antenna mounted properly the range of a 8 foot 6 db gain antenna will be less than 5 miles plus the the range of the other station. So boat to boat about 10 miles on average.

If your transmit range is only five miles, then 5 miles is all you get. VHF radio works on Line of Sight. Your transmission has to reach the antenna of the receiving station. If your range is 5 miles, and another boats range is 5 miles, you talk to each other if you are 10 miles apart. It just does not work that way... Your range is 5 miles, you can talk 5 miles. You might can receive a station farther away, because they have 1. taller antenna, 2. more powerful radio transmission, etc.

There is occasion that due to atmospheric conditions, you can talk great distances, but do not count on it in an emergency...

Can I hide it in my Bimini top? If I put it inside one of the vertical metal tubes that make up the Bimini will it increase my range or decrease it?

The metal tube will cause interference and decrease the range and effectiveness of the radio...

 

[Lyle29464]

Re: Antenna Hidden

it will decrease to zero.

I would go with the flow on this.

 

[The_Kid]

Re: Antenna Hidden

50 watts naa,
50 thousand watts yaa, pumpin the wattage it your cottage.
any one played around with the old an-grc 106 sets?
rob

I never played with any of the low wattage stuff like that. I repaired the AN/TPS-22 radar set. It had a 2 mega watt output.

 

[wizbang 13]

Re: Antenna Hidden

"my wife doesn't like the look" Get a "whipped"antenna

 

[Boatist]

Re: Antenna Hidden

Knightgang
Yes you do get the range of your boat plus the range of the other station added together.
Example my boats range is almost 5 miles but I can talk to the Coast Guard Group San Francisco from 80 miles north.
That is because their antenna is 3000 feet high on top of a mountain and has a range of 77.77 miles plus my 5 miles for a range of 82.77 miles.

To help you understand it draw a circle on a page now with a straight edge draw a straight line just above the circle. The circle is the earth or ocean.
The straight line is the line of site VHF signal.
Now draw boat antenna on each side and you will see that the line of site VHF signal will reach more than my 5 miles.
To add some fun make a second line on one side 10 times as long as the other two lines and you will see that that high monuted Coast Guard can be seen a lot farther away.

Here is a site with the formula to figure distance.

http://www.shakespeare-marine.com/faq2.asp?ReqNum=9

Hope that helps you understand it.

 

[ENSIGN]

Re: Antenna Hidden

Get rid of the old lady so you can enjoy boating!!!

 

[Knightgang]

Re: Antenna Hidden

Boatist, I understand this as I am in the military and am very familiar with how radio communications work. If you can talk to a station that is 80 miles away, then your range (at least in those conditions and with that station) is 80 miles...

The receiveing radio waves do not reach out and grab your transmission waves and pull them back to the antenna, nor do they interpret them in mid air. Your transmission waves have to reach to receiveing antenna to be received.

THe 3000 foot coast guard antenna probably has a range greater than 77 miles. Additionally, with it that high, your antenna has very little abstruction to reach it, therefore, you have Line of Sight and can talk to that station.

Range of radio depends on many factors, not only Line of Sight. The Transmission power has alot to do with how far it can push the transmission waves. Additionally, obstructions such as terrain (mountains) and trees, etc. can reduce range by reducing Line of Sight as well as the radio not having enough power to "Shoot Through" the obstruction.

I have no doubt that you can talk to a station 80 miles away, especially the Coast Guard, but it is not due to the combined ranges of the stations. Also, the Coast Guard may have repeaters set up that relay the signal to extend the range, from their station and for the boaters stations...

 

[Knightgang]

Re: Antenna Hidden

I see Shakespears claim of adding the range of two stations together to get the range between stations. I do not understand why they can make this claim. It makes no sense as the transmitting signal needs to reach the receiveing antenna to be received...

 

[Fl_Richard]

Re: Antenna Hidden

+1 for get rid of the wife!

What marketing person came up with the Shakespeare definition is way off. If the signal never reaches the receiving antenna it cannot be received.

The coast guard can hear very faint signals and they transmit with powerful military transmitters. There receivers are extremely sensitive and they use directional antennas which increase reception signal strength.

 

[Boatist]

Re: Antenna Hidden

Knightgang
Did you make big circle on piece of paper then and then draw a straight line on the top of the circle that touches the circle at the top.
This is the earth and the line at the top is the line of sight signal.
Draw a boat antenna on each side that reaches this line of site signal.
You will be able to see that after a short distance at the top the signal will head out into space and not be able to reach farther around the circle. This is my boats range but if you put a boat on the other side you will see that it's antenna can still reach that line of site signal. This is the other boats range. If it is a sail boat with antenna 30 feet high the range in much greater.
If it is a Coast Guard station with a very high mounted antenna then the range is much greater still.
To be clear I am talking about range over water and the range is limited by the the curvature of the earth and the height of the antenna.
The range has very little to do with power but more power can help you reach your station.
Example that San Francisco Coast Guard station antenna on the 3000 foot high mountain is in range from 82 miles away. (My 5 miles plus their 77 miles)
Their antenna is a very high gain and my antenna is a 6 DB gain.
So even on 1 watt from My radio my Efective Radiated Power (ERP) is 4 watts.
I could likely reach them on 4 watts but since their antenna reaches 77 miles to the North, West, and South it is unlikely they would here me.
On a nice summer weekend with seas 6 feet or less they probably have over 2000 boats is range of their station. While I can only here boats within about 10 miles of my location they car here all those boats. Since most boats are calling other boats on Channel 16 and I can not here them then 25 watts or 100 watts (ERP) is my best hope for them to here me.

I been in Radio since High School where I built my first two CB Radios. Then in the Air Force durning Viet Nam and earned my living in Electronics Since 1967. Had a Ham Licence Since 1973. Completed a Master course in Commuincation Electronics in 1974. Still today I like to help Boater solve radio problems. When we go to the a Pacific Ocean Camp Ground at Bodega Bay I always take all my radio test gear, 50 foot of coax cable and have help a Lot of Boater solve their radio problems. I really like helping boater with their radio problems after we get the fish cleaned at the end of the day.
If you search around the net their are many site that will have pictures and diagrams to explain VHF Line of Site communictions.

 

[Knightgang]

Re: Antenna Hidden

I understand LOS communications. I am a secondary specialist in Communications in the military. As a Forward Observer (primary) I am all alone at times with just my team and communication to keep me alive.

All I am saying is that radio signals are not interpreted in mid air. Meaning that a TRANSMITTED signal has to be able to reach the receiving Antenna to be heard. Therefore, you cannot ADD individual range of two different stations (say 10 miles each) to get a total talk range between those two stations of 20 miles. If one radio will only reach 10 miles, then the range between the two is 10 miles...

VHF is used for marine radios because of the distance the wavelength can travel given unobstructed terrain (open ocean) with the least interference without a great deal of power... Yes, antenna height has alot to do with the range based upon its height above the surface, just as the transmitted wattage plays a role in range by producing a stronger signal that will carry a greater distance without diminishing (becomming unorganized, broken and un readable). But regardless, you still cannot get around the fact that the transmitted signal has to be able to reach the receiving station to be heard...

Alot like a soccer game. Say that two teams are playing soccer and each player is capable of kicking the ball half the length of the field. However, in this game, all of the players have to stay within their own goalie box. Given this, neither team will be able to score. If each team were given a ball, and they kicked the ball, the balls would cross, but neither ball would reach the other goal. That is what the radio signals are like. They have to reach the receiving station to score (be interpretted and heard)... Therefore, the range between two stations is only as great as the shorter range of the two...

 

[Boatist]

Re: Antenna Hidden

The transmited signal of the first boat does reach the antenna of the second boat. If it did not then it would not be heard.

The circle with a straight line at the top shows this very clear.
The first boat transmits with and antenna 11 feet above the water and his range is 4.71 miles. The radio signal travels in a straight line and with a 11 feet high antenna the max distance that the signal can reach the surface of the water is 4.71 miles. The radio wave continues on in a straight line and heads out into space so no longer reaches the surface of the water. So the first boats range is 4.71 miles. The second boat over the horzion can still hear the first boat because his antenna is above the surface of the water and can see the first boats antenna. If his antenna is also 11 feet above the water then his antenna can see your antenna for another 4.71 miles. So the range between boats is 9.42 miles. If his antenna is higher then his antenna can see your antenna even farther. So the range of each boat is 4.71 miles and the two boat can talk up to 9.42 miles.

Even a lot more power would not increase the range more than a tiny bit over the ocean because the line of site signal would not hit the other antenna. Now close to shore there are thing that can increase the range with more power. These would be things the signal would hit up on a mountain and bounce off. Since that reflected signal is much higher it can increase the range. Since the max power is 25 watts this really does not happen much.

Example a EPIRB transmits about .1 watts or 1/10 of a watt of power and is a frequency that is also line of site. Even with 1/10 of a watt it sends your position to Sattelites 500 to 600 miles high in earth orbit.

Below are a couple more sites with good information.

First one has a chart showing range between stations. Note if either boat has a higher antenna then the range increases.

Second one has a place for the height of first antenna then the height of the second antenna and it will give you the distance.

http://www.westmarine.com/webapp/wcs/stores/servlet/westadvisor/10001/-1/10001/VHF-Antennas.htm

http://www.naval.com/sight/index.htm

 

[Knightgang]

Re: Antenna Hidden

The very first line in your last post is exactly what I have been trying to say. The transmitted signal has to be able to reach the receiving station to be heard. You agreed to the same saying that it does.

I think the issue is cleared up with your second link. However, they are refering to Radio Horizion, which is what you have been calling Range. Two different Things...

Radio Horizon has to do with the curvature of the Earth and the expected line of sight, but it is not the range, as you have been refering to it...

I think we have been trying to say the same thing, using different terminology. Hopefully this will clear it up for those that have gotten confused...

 

[Boatist]

Re: Antenna Hidden

I glad we finally agree that you have to add the range of the two boats together to get the max distance they can talk to one another,
and also each boats range to the hozrion is based on antenna height.

 

[Knightgang]

Re: Antenna Hidden

I still submitt that the radio Horizon and the Range are two different things. Yes the Horizons need to be added, but the range it totaly different. It factors into the range, but it is not the range...

I do not want someone to think that if they have an 8' antenna, that is mounted with a total height of 11' above the water, that they can only talk 5 miles. That is not true. If the height of the receiving station is higher than theirs, then they can talk further than that...

Ocean Fishing boats can talk hundreds of miles across open ocean...